Ching-Wen Chen

A power efficiency routing and maintenance protocol in wireless multi-hop networks

In wireless multi-hop networks, selecting a path that has a high transmission bandwidth or a high delivery rate of packets can reduce power consumption and shorten transmission delay during data transmission. There are two factors that influence the transmission bandwidth: the signal strength of the received packets and contentions in the contention-based MAC layer. These two factors may cause more power to be consumed during data transmission. We analyze these two factors and propose a power-aware routing protocol called MTPCR. MTPCR discovers the desired routing path that has reduced power consumption during data transmission. In addition to finding a desired path to reduce power consumption, MTPCR also takes into account the situations in which the transmission bandwidth of the routing path may decrease, resulting in much power consumption during data transmission because of the mobility of nodes in a network. MTPCR is thus useful in a network: it analyzes power consumption during data transmission with the help of neighboring nodes, and it uses a path maintenance mechanism to maintain good path bandwidth. The density of nodes in a network is used to determine when to activate the path maintenance mechanism in order to reduce the overhead of this mechanism. With the proposed path maintenance mechanism, power consumption during data transmission can be efficiently reduced, as well as the number of path breakages. In our simulation, we compared our proposed routing protocol, MTPCR, with the following protocols: two classical routing protocols, AODV and DSR; two power-aware routing protocols, MMBCR and xMBCR; and one multiple path routing protocol, PAMP. The comparisons are made in terms of throughput of the routing path, power consumption in path discovery, power consumption in data transmission, and network lifetime.

Signal strength based routing for power saving in mobile ad hoc networks

The transmission bandwidth between two nodes in mobile ad hoc networks is important in terms of power consumption. However, the bandwidth between two nodes is always treated the same, regardless of what the distance is between the two nodes. If a node equips a GPS device to determine the distance between two nodes, the hardware cost and the power consumption increase. In this paper, we propose using a bandwidth-based power-aware routing protocol with signal detection instead of using GPS devices to determine the distance. In our proposed routing protocol, we use the received signal variation to predict the transmission bandwidth and the lifetime of a link. Accordingly, the possible amount of data that can be transmitted and the remaining power of nodes in the path after data transmission can be predicted. By predicting the possible amount of data that can be transmitted and the remaining power of nodes after data transmission, we can design a bandwidth-based power-aware routing protocol that has power efficiency and that prolongs network lifetime. In our simulation, we compare our proposed routing protocol with two signal-based routing protocols, SSA and ABR, and a power-aware routing protocol, MMBCR, in terms of the throughput, the average transmission bandwidth, the number of rerouting paths, the path lifetime, the power consumed when a byte is transmitted, and the network lifetime (the ratio of active nodes).

Design of a low power and low latency MAC protocol with node grouping and transmission pipelining in wireless sensor networks

In wireless sensor networks (WSNs), the strategies of periodical sleep and contention to use the channel for transmission are efficient in terms of power consumption and channel utilization. However, contention and sleep cause other power consumption problems, namely the overhearing of the control packets and increased transmission latency. In this paper, we propose the use of node grouping and transmission pipelining to reduce power consumption and transmission delay. In the design of node grouping, there are several groups in a WSN, where nodes in different groups wake up at different time. Each sensor node is initially set to belong to one of these groups. In contrast to the situation in which all nodes hear the control packets during the contention period, node grouping reduce the number of nodes that overhears the control packets at the same time to reduce power consumption, To establish communication between nodes belonging to different groups, we assign a group table to each node. The group table recodes the group indices of all the neighbors of that node. With looking up a group table in a sensor node, a sender can wake up at the group time of the receiver. As a result, two nodes belonging to different groups can communicate with other. With regard to transmission delay of a multi-hop path in WSNs, if a sender transmits data to the receiver and the receiver cannot send the data to the next receiver right now, the transmission delay increases. To reduce the transmission delay, we propose the transmission pipelining method. Transmission pipelining makes the group number of the nodes on a path to be continuous. Therefore, the sensor node is thus able to transmit data to the sink node pipelining. From the simulation results, when the number of groups is 2, the power consumed in transmitting a byte (mJ/byte) and the transmission delay in our proposed design are better than those of SMAC by about 50%. When the number of groups is 4, although the transmission delay is only a little better than that of SMAC, the power consumed in transmitting a byte in our proposed design is much less than the power consumed in SMAC by 75%.

Design schemes of dynamic rerouting networks with destination tag routing for tolerating faults and preventing collisions

In fault-tolerant multistage interconnection design, the method of providing disjoint paths can tolerate faults, but it is complicated and hard to choose a collision-free path in disjoint paths networks. A network with disjoint paths can concurrently send more identical packets from the source node to increase the arrival ratio or backtrack a packet to the source and take the other disjoint path, but these two methods might increase the collision ratio. In contrast, a dynamic rerouting method finds an alternative path that tolerates faults or prevents collisions. In this paper, we present methods of designing dynamic rerouting networks. This paper presents (1) three design schemes of dynamic rerouting networks to tolerate faults and prevent collisions; (2) design schemes that enable a dynamic rerouting network to use destination tag routing to save hardware cost in switches for computing rerouting tags; (3) a method to prevent a packet from re-encountering the faulty element again after rerouting to reduce the number of rerouting hops and improve the arrival ratio; and (4) simulation results of related dynamic rerouting networks to realize the factors which influence the arrival ratio including the fault tolerant capability and the number of rerouting hops. According to our proposed design schemes and according to our analysis and simulation results, a designer can choose an applicable dynamic rerouting network by using cost-efficient considerations.

A minimum transmission energy consumption routing protocol for user-centric wireless networks

In this paper, we propose a minimum transmission energy consumption (MTEC) routing protocol that reduces energy consumption and prolongs network lifetime in user-centric wireless networks. MTEC is proposed for selecting the minimum transmission energy consumption path for data transmission based on the proportion of successful data transmissions, the number of channel events, the remaining node energy of nodes, and the traffic load of nodes. The simulation results showed that our proposed MTEC provided better packet delivery rate and throughput than DSR and TSA. MTEC also exhibited lower energy consumption during data transmission and a higher network lifetime than existing protocols.

A Bandwidth-Based Power-Aware Routing Protocol with Low Route Discovery Overhead in Mobile Ad hoc Networks

In the design of power-aware on-demand routing protocols in mobile ad hoc networks, it must be taken into account that nodes may use a great amount of power to find the desired routing path during the path-discovery phase. In addition, in previous research on power-aware routing protocols, the path bandwidth was often not considered. In this paper, we tackle these issues by proposing a power-aware routing protocol with low route requests (LRR) to find a path with high path bandwidth. By making a low number of routing requests (RREQs), mobile nodes help to broadcast the routing request only when they first receive the routing requests. In addition, based on the receipt of the routing requests from the neighboring nodes, mobile nodes record the location information of its one-hop neighboring nodes. In the path-reply phase, mobile nodes in the found path use the collected location information of their neighbors and our proposed relay model to modify the found path so that the found path has high bandwidth. In our simulation, we compared our proposed routing protocol (LRR) with ad hoc on-demand distance vector, dynamic source routing and min–max battery capacity routing in terms of the following: power consumption in the path-discovery phase and the path-reply phase, bandwidth of the found path, power consumed during data transmission and overall power consumption. In addition, we compared our two proposed routing protocols, the minimum power consumption routing protocol that selects one path with minimum transmission power from all paths and the LRR routing protocol, in terms of the following: the power consumption in the path-discovery phase, the path bandwidth and the overall power consumption. From the simulation results and the analysis, we can see that the proposed LRR routing protocol that uses a low number of routing requests and our proposed relay model to improve path bandwidth can efficiently reduce the overall power consumption.

Bandwidth-based routing protocols in mobile ad hoc networks

In this paper, we propose a high performance routing protocol and a long lifetime routing protocol by considering the fact that the bandwidth between two mobile nodes should be different when distances are different. In the high performance routing protocol, to reduce the number of rerouting times, we take the bandwidth issue into account to choose the path with the capability to transmit the maximum amount of data with the help of the GPS. With exchanging the moving vectors and the coordinates of two adjacent mobile nodes, the possible link lifetime of two adjacent mobile nodes can be predicted. Subsequently, a path with the maximal amount of data transmission can be found. With regard to our proposed long lifetime routing protocol, to maximize the overall network lifetime, we find a path with the maximal remaining power after data transmission. With the link bandwidth and the desired amount of data transmitted, the consumption power is computed to obtain the remaining power of a mobile node. Accordingly, we can choose the path with the maximal predicted remaining power to maximize the overall network lifetime. In the simulation, we compare our high performance routing protocol with the AODV and LAWS in terms of throughput, rerouting (path breakage), and route lifetime. With respect to power consumption, we compare our proposed power-aware routing protocol with the POAD and PAMP in terms of the overall network lifetime and the ration of survival nodes to the all nodes.

Design of a Low-Power and Low-Latency MAC Protocol with Nodes Grouping and Transmission Pipelining in Wireless Sensor Networks

In wireless sensor networks (WSNs), the strategies of periodical sleeping and contending for using the channel are efficient in power consumption and channel utilization. However, the situations of contention and sleep arise another power consumption problem of overhearing the controls packets and increasing transmission latency. In this paper, we propose the design of nodes grouping and transmission pipelining to improve the power consumption and transmission delay. In nodes grouping design, there are several groups in the WSNs and each sensor node is initially set to belong to one of these groups where each group has different contention time and transmission time. In contrast to the situation that all nodes hear the control packets in the contention period, nodes grouping can reduce the number of nodes that overhearing the control packets in the same time to save the power consumption. To improve the transmission delay, we propose the design of transmission pipelining that makes the group number of the nodes on the path to be continuous. Therefore, the sensor node can transmit data to the sink node pipelining. From the simulation results, when the number of groups is 2, the power consumption of transmitting a byte (mJ/byte) and the transmission delay of our proposed design perform better than SMAC by about 50%. When the number of groups is 4, although the transmission delay shows only a little better than SMAC, the power consumption of transmitting a byte of our proposed design has much better than SMAC by 75%.

A tagless cache design for power saving in embedded systems

In embedded systems, cache is commonly used to improve system performance. However, the cache consumes a large amount of power, and among the components of the cache memory, tag comparisons consume the most amount of power. Therefore, how to design a cache that does not consume so much power when comparing tags and that has a high hit ratio is an important challenge. In this paper, we propose a Tagless Instruction Cache, called TL-IC, that does not perform tag comparisons in order to save power in embedded systems. To guarantee that an instruction fetched from TL-IC is the desired instruction, instead of cache lines being used, the basic blocks of programs are placed into TL-IC. In addition, to utilize TL-IC as much as possible in order to save the most amount of power and to take into account the general-purpose and special-purpose applications, both the static allocation and the dynamic allocation of basic blocks are used to select the frequently executed basic blocks of programs in TL-IC. With a high utilization of TL-IC that does not perform tag comparisons, the power consumed in fetching instructions can be efficiently reduced. In the simulation results, we show and compare the power consumption of our proposed TL-IC, L0 cache, Linebuffer, and TH-IC.

An overlapping and pipelining data transmission MAC protocol with multiple channels in ad hoc networks

In mobile ad hoc networks (MANETs), the IEEE 802.11 DCF protocol is commonly used at the medium access control (MAC) layer to reduce collision and contention. However, mobile nodes, before send out data, need to wait for other in-process data transmission in the same range to be completed. In this paper, we address this performance degradation problem in the DCF mechanism and propose an overlapping and pipelining data transmission MAC protocol to enhance throughput. The protocol regulates the actions of the neighboring nodes of both the sender and the receiver and enables the utilization of the same channel simultaneously by these neighboring nodes. A multiple sub-channel technique is proposed to avoid the interference problem caused by the control and data signals of different communication mobile node pairs. With the regulated actions and the multiple channel technique, multiple pairs of mobile nodes are provided with the desired feature of utilizing the same data sub-channel simultaneously without interfering with one another. Although the overlapping data transmission technique can increase the number of simultaneous communication pairs, an efficient bandwidth allocation of the control and data sub-channels to maximize utilization is critically important. Therefore, we further propose a bandwidth allocation strategy in which the control signals and data signals are pipelined. Performance simulation results prove the efficiency of the proposed bandwidth allocation strategy with better channel utilization. In addition, the proposed MAC protocol with the bandwidth allocation strategy, combined with the overlapping and pipelining data sub-channel technique, outperforms the IEEE 802.11 DCF in throughput (kB/s) by about 43.76%.